50 subsequent subjects (Group B) for each regimen will be screened simultaneously, with no more than 10 subjects enrolled for each regimen in Group B prior to the completion and analysis of Group A. These subjects will also be recruited from either site. Group B subjects will have one or two sampling visits with 1 to 4 blood samples obtained at each visit, with a stored sample for future genotyping obtained on one of the visits. Samples will be collected just prior to a dose, at 2 hours, between 4 and 6 hrs, and between 10 and 14 hours after a medication dose. These visits may coincide with the subjects' regularly scheduled visit to the clinic, or be scheduled separately, depending on the preference and availability of the subject.